PIE (Principle of Inclusion-Exclusion) |AUB=A+|B|-A∩B AUBUC=A+B+C -A∩B-A∩C-B∩C +AnBnC C BnC AnC AnBnC B AnB PIE (Principle of Inclusion-Exclusion) |A ￾ B| = |A| + |B| ￾|A ⇥ B| |A ￾ B ￾ C| = |A| + |B| + |C| ￾|A ⇥ B| ￾ |A ⇥ C| ￾ |B ⇥ C| +|A ￾ B ￾ C|